1. Field of the Invention
This invention relates to amino-functionalized iodothyronine derivatives, immunogen conjugates comprising such derivatives coupled to conventional immunogenic carrier materials, and anti-iodothyronine antibodies prepared against such immunogen conjugates. Such antibodies are useful in immunoassays for determining iodothyronines in biological fluids. The amino-functionalized derivatives are also useful in preparing labeled iodothyronine conjugates for use in such immunoassays, particularly those of the nonradioisotopic type.
The iodothyronines have the following general formula: ##STR1## wherein .beta..sup.1 and .beta..sup.2 are, independently, hydrogen or iodine. The iodothyronines of clinical interest are listed in the following table:
______________________________________ Iodothyronine .beta..sup.1 .beta..sup.2 ______________________________________ 3,5,3'5'-tetraiodothyronine iodine iodine (thyroxine; T-4) 3,5,3'-triiodothyronine iodine hydrogen (liothyronine; T-3) 3,5',5'-triiodothyronine hydrogen iodine ("reverse" T-3) 3,3'-diiodothyronine hydrogen hydrogen ______________________________________
The quantitative determination of the concentration of the various iodothyronines, particularly the hormones T-3 and T-4, in serum and of the degree of saturation of the iodothyronine binding sites on the carrier protein thyroid binding globulin (TBG) are valuable aids in the diagnosis of thyroid disorders.
2. Brief Description of the Prior Art
Iodothyronines have been derivatized in many different ways in coupling them to immunogenic carrier materials for the purpose of preparing immunogen conjugates. Antibodies prepared against such conjugates are used in immunoassays for determining iodothyronines. Also, iodothyronines have been variously derivatized in order to couple a desired labeling moiety yielding a labeled conjugate useful in such immunoassays.
The commonly used technique for preparing iodothyronine immunogen conjugates involves coupling the iodothyronine directly through its available amino and carboxyl groups to amide bond carboxyl and amino counterpart groups on the carrier material in the presence of carbodiimide. A mixture of conjugates is obtained and consequently a mixture of anti-iodothyronine antibodies are obtained. See Gharib et al., J. Clin. Endocrinol 33:509(1971).
U.S. Pat. No. 4,171,432 describes the coupling of a ribonucleotide to iodothyronines through the carboxyl group. U.S. Pat. No. 4,040,907 describes the coupling of enzymes with iodothyronine derivatives derivatized at the phenolic hydroxyl group.
The preparation of aminoacyl thyroxine derivatives derivatized at the amino group of thyroxine is described in Endocrinol. 89:606-609(1971).